Remove unused class DelegatingActionListener (#36257)

server/src/main/java/org/elasticsearch/action/support/DelegatingActionListener.java

@@ -1,48 +0,0 @@
-/*
- * Licensed to Elasticsearch under one or more contributor
- * license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright
- * ownership. Elasticsearch licenses this file to you under
- * the Apache License, Version 2.0 (the "License"); you may
- * not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-
-/*
- * A Simple class to handle wrapping a response with another response
- */
-package org.elasticsearch.action.support;
-
-import org.elasticsearch.action.ActionListener;
-import org.elasticsearch.action.ActionResponse;
-
-public abstract class DelegatingActionListener<Instigator extends ActionResponse, Delegated extends  ActionResponse>
-        implements ActionListener<Instigator> {
-
-    ActionListener<Delegated> delegatedActionListener;
-
-    protected DelegatingActionListener(final ActionListener<Delegated> listener) {
-        this.delegatedActionListener = listener;
-    }
-
-    protected abstract Delegated getDelegatedFromInstigator(Instigator response);
-
-    @Override
-    public final void onResponse(Instigator response) {
-        delegatedActionListener.onResponse(getDelegatedFromInstigator(response));
-    }
-
-    @Override
-    public final void onFailure(Exception e) {
-        delegatedActionListener.onFailure(e);
-    }
-}